Hen lifecycle

Which came first, the chicken or the egg?

In Australia the most common breeds of layer hens used in commercial scale egg production are the Hy-Line Brown, ISA Brown and Hi-Sex Brown. Technical aspects aside, these birds are brown in colour with a red comb and have been genetically selected to lay as many eggs as possible over their relatively short life.

Life for the vast majority of hens begins at a breeding unit.

To begin, fertilised eggs are imported into Australia and are hatched as breeding birds (male and female lines). After a fairly complicated breeding process, eggs are laid and then transferred to industrial-size incubators.

These incubators can be huge and consist of shelves that can hold tens of thousands of eggs at a time. They have strictly controlled temperature, humidity, and ventilation. Incubation normally takes around 21 days.

Following the incubation period, around 24 million chicks will hatch each year - and at 1 day old their sex is determined. Sexing chicks requires considerable skill and is done at this very early stage to determine their fate.

If strong and healthy, female chicks are transferred to a 'rearing' facility , where they are grown to a certain age before being moved again to a laying facility - which could be a cage, free range or barn system. It's only the female chicks that hatch from these incubated eggs that will become commercial layers that produce the eggs we eat.

The male chicks that hatch are considered an unwanted by-product of egg production and are killed and disposed of shortly after hatch.

Male chicks are killed for two reasons: firstly they can't lay eggs and secondly they aren't suitable for chicken-meat production. Remember layer hens - and therefore their chicks - are a different breed of poultry to chickens that are bred and raised for meat production.

From the hatchery, the female chicks are transferred to rearing facilities where they are raised in either sheds or cages - depending on what kind of production system they will be housed in when they're ready to lay. The chicks will remain here until they are about 17 weeks old.

Once they have reached appropriate body weight they are exposed to increasing lengths of light in the sheds (typically 16 hours) in order to stimulate egg production. Altering light can affect chickens activity levels, sleep levels, and behaviour. 

At around 17 weeks of age hens are ready to start laying eggs and will spend their lives in either a cage, barn or free range system. The vast majority of hens in Australia live in cage systems.

Hens will lay about 300 eggs each year and will produce eggs up until around a year and a half of age. From here, their ability to produce eggs will decline. 

Over 11.3 million hens live in cages.  They are also known as 'battery' cages because of the way they are stacked upon each other over multiple rows in a single shed containing up to 100,000 hens.

Hens in cage systems spend their entire life in a metal cage, and share their space with three to seven other hens. 

In 2008, the size of cages and space for each hen increased very slightly (about the size of coaster) under the Model Code, however despite this change, each hen is still only allowed the space of less than an A4 sheet of paper.  

Modern cage facilities have automated feed and watering systems, ventilation, lighting, and manure and egg collection via conveyor belt systems.

Although the cage industry may argue their systems are more easy to manage, more hygienic and have lower rates of disease and infections, hens in these systems have a miserable existence as a result of restricted movement, lack of exercise, inappropriate flooring (wire mesh), and ongoing stress and frustration due to their inability to express the natural behaviours essential to them.

Basic needs such as perching, nesting, foraging, dust bathing and stretching or flapping wings aren't available to hens in cages. 

Furnished cages are similar to conventional cages. They were developed as an alternative to the traditional cage system with the aim of providing more space and height, as well as additional provisions such as nests, litter, scratching pads ( to help shorten claws), and perches.

Their size may vary, housing between 10 to 60 birds. A relatively new system, these furnished cages are found in the European Union, however aren't in use in Australia.

In a barn system, hens aren't kept in cages but instead can move about in large sheds. Around 1 million hens are housed in barn systems in Australia. Flocks may be between 500 and 5,000 birds.

Sheds are normally equipped with an automated feeding and watering system, and eggs are collected mechanically.

Hens in barn systems can carry out natural behaviours such as stretching and flapping wings. All barns have nest boxes where hens can lay their eggs but not all barns have perches or litter which are key to catering to hens behavioural needs (some barns have slats or wire-mesh flooring).

Barn-laid eggs are a good alternative to cage eggs. A well-managed barn can be just as welfare friendly for a hen as a proper free-range facility. From an animal welfare perspective it's a myth that barn is second best. It's all about who is operating the system and to what standards they adhere.

Many eggs are now being marketed as cage-free. Essentially, cage-free eggs are barn-laid eggs.

The RSPCA approves some barn laid hen farms under the RSPCA Approved Farming Scheme.

There are around 4.5 million hens in free-range systems in Australia. Conditions on free-range farms vary greatly, but most importantly hens aren't confined to cages.  

In a well-managed free-range system hens should have access to an attractive outdoor area during the day including shade and protection. At night, large flocks of free-range hens are usually kept in sheds or barns to keep them safe from predators, while smaller flocks may be kept in smaller, possibly moveable sheds.

Free-range hens can dustbathe, scratch and forage, and lay their eggs in a nest. Some free-range systems provide perches for hens to roost when they are inside at night.

The RSPCA believes it's important that layer hens in free-range systems are well managed, have access to appropriate shelter, and are provided with a suitable range area which they readily use.

The RSPCA approves some free range hen farms under the RSPCA Approved Farming Scheme.

Although hens have a natural lifespan of up to 12 years, their ability to produce eggs declines at around 72 weeks of age and as a result, commercial hens of this age are considered less profitable.

Sometimes commercial hens are put through a process of 'forced moulting' which extends their ability to produce eggs. Moulting is a natural process, allowing hens' bodies to rest and rebuild bone strength. In commercial systems however, moulting is carried out using feed withdrawal or non feed withdrawal methods. Particularly for those birds that have feed withdrawn (for a period up to 2 weeks), forced moulting represents a serious welfare issue. Where feed isn't withdrawn, the bird's diet is changed to a feed low in energy and protein. Both methods cause a marked reduction in body weight but also re-invigorates egg production.

Where hens aren't forced to moult, they're considered 'spent' and are removed from production.

The process of removing 'spent' hens is known as 'depopulation' where hens are manually caught by human 'catchers' (up to 5 hens per hand) and placed into crates ready for transport.

There can be welfare issues during depopulation, often time pressures and rough handling can lead to injury such as bone fractures. Fracture rates tend to be higher in cage systems during depopulation, mainly because of the risks and difficulties involved in removing birds through narrow cage doors.

At the slaughtering plant, hens are removed from their crates and shackled, upside down, by their legs on a conveyor system. They are then stunned using the most common method in Australia which is through an electrical water bath and have their necks slit by a sharp rotating blade.

Hens are then plucked, cleaned, processed and packed for further distribution. Carcasses are used for manure and fertiliser, pet food, and lower-quality processing meat for human consumption such as in soups and stocks.